1. Field of the Invention
The present invention relates to a battery cell, and particularly to a method for forming low-resistance electric connection points for a battery cell with two external nickel electrode terminals.
2. Description of the Prior Art
A battery pack usually consists of hundreds or even thousands of serially or parallel connected battery cells. The electric connection among the battery cells is achieved by welding metal plates to the electrode terminals of the battery cells, and then the metal plates electrically connect the battery cells together. Hence, the conductivity of the electrical welding points has great influence on the conductivity of the entire loop of the battery pack. However, the electrode terminals of the battery cells are very likely to be oxidized and covered with impurities since they are external terminals exposed to atmospheric environment containing moisture and impurities. The oxides and impurities on the electrical terminals will produce a contact resistance, which will have a direct influence on the conductivity, and deteriorate the discharge and conductivity performance of the battery pack.
A conventional electrical connection method for connecting battery cells 10 is shown in FIGS. 1 and 2, wherein the battery cells 10 each have a positive electrode terminal 11 and a negative electrode terminal 12 which are made of nickel, and then the battery cells 10 are connected in series by nickel plates 20 connected between terminals 11, 12 of different polarity of the battery cells 10, and the battery cells 10 can be connected in parallel by connecting the nickel plates 20 between the terminals of the same polarity.
The nickel plates 20 are spot welded to the positive or negative electrode terminals 11, 12, which requires high temperature to melt the nickel plates 20 and the electrode terminals 11, 12 of the battery pack, meanwhile, the nickel plates 20 are pressed onto the electrode terminals 11, 12, and the nickel plates 20 and the electrode terminals 11, 12 must be welded for several times to form several weld spots 21, so that the nickel plates 20 and the electrode terminals 11, 12 are fixed together by the weld spots 21. Namely, the nickel plates 20 and the electrode terminals 11, 12 are connected by the weld spots 21, however, the connecting area of the weld spots 21 is too small, which results in a high resistance, and accordingly affects the discharge and conductivity performance of the battery pack.
Furthermore, spot weld requires professional skill since the welding temperature and pressing force for pressing the nickel plates 20 and the electrode terminals 11, 12 need to be precisely controlled in order to obtain a reliable and low resistance welding connection.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.